How many #8 THHN fit in 1-1/2" PVC Sch 40?
218 AWG THHN/THWN-2 wires in 1-1/2" Rigid PVC conduit, Schedule 40
1.986 sq in × 40 % = 0.7944 sq in allowed. ÷ 0.0366 sq in per wire = 21.70, so 21.
This pull in numbers
- 21 wires fill
- 38.7 % of 1-1/2" PVC Sch 40
- Limit for three or more
- 40 %
- For 22 or more
- 2" PVC Sch 40, up to 36
- Pipe to wire diameter
- 7.36 to 1
- In THW insulation
- 18 fit
- In XHHW-2 insulation
- 18 fit
Before you pull 21
- The ground counts. Every wire in the pipe counts toward fill, the green or bare ground and the neutrals too. 21 is the total, not the hots.
- Derating. If all 21 were current-carrying, each would be adjusted to 45 % of its ampacity (Table 310.15(C)(1)): a #8 THHN at 55 A in the 90 °C column becomes 24.8 A. Grounds don't count as current-carrying. How derating works
- Bends. A full pipe pulls hard. Keep to 360° of bends between pull points, less for a tight fill.
#8 THHN in other 1-1/2" conduit
| Conduit | Inside area | Most #8 THHN |
|---|---|---|
| Electrical metallic tubing | 2.036 | 22 |
| Intermediate metal conduit | 2.225 | 24 |
| Rigid metal conduit (RMC, GRC) | 2.071 | 22 |
| Rigid PVC conduit, Schedule 40 | 1.986 | 21 |
| Rigid PVC conduit, Schedule 80 | 1.711 | 18 |
| Flexible metal conduit (FMC, Greenfield) | 1.858 | 20 |
| Liquidtight flexible metal conduit (LFMC) | 1.981 | 21 |
| Electrical nonmetallic tubing (smurf tube) | 1.986 | 21 |
#8 THHN in other PVC Sch 40 sizes
Other wire sizes in 1-1/2" PVC Sch 40
#14: 82#12: 59#10: 37#8: 21#6: 15#4: 9#3: 8#2: 7#1: 5#1/0: 4#2/0: 3#3/0: 3#4/0: 1250 kcmil: 1300 kcmil: 1350 kcmil: 1500 kcmil: 1